This invention relates generally to test equipment that is used in conjunction with demand recorders. More specifically, this invention is directed to a test counter intended for use for demand recorders which accumulate data related to a power distribution network at a remote field installation such as the Westinghouse WR-2C and WR-4C demand recorders. These recorders are used to collect data over an extended period of time at a field installation and preserve that data for later analysis.
Demand recorders are utilized under a variety of circumstances. As an example, power companies utilize demand recorders to measure and accumulate data relating to various environmental parameters so that anomalies that may occur on a power grid can be correlated with physical phenomena. This type of information can be used to advantage in determining problem areas within a power network or the effect of various environmental parameters. Typically, a demand recorder is installed at a field location remote from a central facility. The recorder is operated over an extended period of time converting analog data into digital pulses. These pulses are recorded on a magnetic tape cartridge. After a predetermined number of days such as, for example, 15 days, the cartridge is extracted by service personnel and replaced with a blank one. The extracted cartridge is taken to the central facility where the data previously recorded is read from the magnetic cartridge and processed into a form meaningful to a human. Specifically, information stored on the tape is in the form of pulses recorded during various predetermined intervals of time. In processing the data at the central facility, the cartridge tapes are played (read) and the number of pulses occurring during predetermined intervals of time are counted. In doing so, analog data originally used to generate the pulses is reconstituted. One problem with this type of demand recording and reading is that there is a lengthy time period covered by the data accumulation and processing procedures. There is no instant feedback to any service personnel indicating when a demand recorder is not properly functioning. It may become apparent upon playback of the data that a demand recorder had not functioned properly over a 15 day period. However, once having learned this, it is impossible to go back and accumulate the data that has been lost by the malfunction. Therefore, it has become common practice with service personnel to make periodic checks of the demand recorders using equipment known as a test counter. Test counters in common use, when attached to a demand recorder, verify that pulses are being recorded. Furthermore, they correlate the number of pulses recorded during a predetermined time interval with a particular analog parameter being measured and represented by those pulses. This insures that there is a desired proportional relationship between the number of pulses and the parameter of interest.
Test counters in common use suffer various operational disadvantages. For example, they are capable of measuring pulse data on only one channel at a time. In some monitoring situations, a plurality of demand recorders are utilized to collect and preserve data. In order to test the demand recorder installation, it would be necessary to attach the test counter to each of the demand recorders for an interval of time, such as 15 minutes and count the pulses recorded. For example, where four demand recorders are installed, the test counter must first be attached to the first counter and allowed to record pulses being generated for 15 minutes. Then, service personnel must detach the test counter from the first demand recorder, read the accumulated count, reset the test counter and then attach it to the second demand recorder. The test counter must then remain attached for a predetermined interval of time such as 15 minutes to count the number of pulses generated and being recorded on the second demand recorder. Then service personnel must detach the test counter from the second demand recorder and attach it to the third, etc. The required service time is even further increased when multiple channels on each demand recorder are utilized. Typically, for an installation using four demand recorders, each having three channels, it would take approximately three hours to test the entire installation, assuming a 15 minutes count time for each channel. It is possible to reduce this time somewhat by using multiple test counters simultaneously. However, the field installations are usually at remote locations and it is difficult to carry very much test equipment to a particular remote installation. Thus, there is a trade-off between the amount of equipment to be hauled to a remote location and the time it takes to conduct a test.
Another disadvantage with the operation of conventional test counters is that they require the attention of the operator during a test. It is necessary for the operator to start the test counter and then to stop it after a predetermined period of time has run. If the operator does not stop the recordation at the predetermined time, the test results will be inaccurate. The information is carried in the form of pulses per unit time. Therefore, the unit time must be controlled. Thus, service personnel must stop and start the counter for each channel of each demand recorder. This requires a significant amount of attention on the part of service personnel and prevents them from carrying any other tasks at the field installation.